1. Field of the Invention
This invention relates to an electrode plate for use in a display device provided with electrodes, for example, a liquid crystal display device. More specifically, the invention relates to an electrode plate for a color display device, which has a color filter made of an organic resin and colored by dyestuff or pigments, in which transparent electrodes and a metal conductor are formed over the color filter.
2. Description of the Prior Art
In recent times, there has been a trend toward increasing the screen size and the pixel density of liquid crystal displays. For this reason, the pitches of pixel arrangement and terminal sections are becoming finer; for example, as fine as 100 to 300 .mu.m. This trend has been accompanied by efforts to reduce the thickness of the displays. At the same time, however, difficulties have been encountered in the connecting of the display to the drive circuit therefor. For this reason, what is commonly termed as the chip-on-glass (COG) method has come into use, in which a display drive IC is directly mounted on the base plate (i.e., a glass plate usually 1 mm in thickness) of the liquid crystal display, as well as an alternative method in which a soldering is used for the connection to improve the reliability.
Even with a prior art display device, a black matrix is sometimes provided on the base plate. In this case, a black matrix formed with a coating of pigments or dyes to a thickness of as little as 1 .mu.m, which is required for a color filter, is not sufficient for obtaining a satisfactory light-blocking performance, with the result that the pixel aperture factor cannot be reduced.
It may be conceivable to form a black matrix with a metal layer. In this case, a sufficient light-blocking performance may be obtained. However, electric short circuit between a metallic chromium thin film and a transparent electrode formed on color filter is liable to be caused through defects in a color filter layer. Therefore, the employment of a metallic layer as a black matrix is infeasible for electrode plate of a simple matrix type liquid crystal display device. Further, such a layer does not act as a conductor. A chromium film formed by sputtering is conceivable as a metallic thin film. This film, however, offers resistance higher by one or more digit places than the resistance of bulk, thus hindering the performance thereof.
Further, where color filters are provided after the deposition of a metal conductor, the metal conductor is attacked when patterning the color filters and transparent electrodes. This often results in degradation of the quality of the metal conductor. This means that bonding failure due to contamination of the metal conductor surface may be frequently occurred at the time of soldering or bonding at terminal sections. Further, the manufactures of both of the metal conductor and transparent substrate are performed in vacuo, while the manufacture of the color filter is performed by printing. This means that it is necessary to conduct a sequence of the manufacturing operation first in vacuo, then in the atmospheric pressure and finally in an evacuated atmosphere. The printing operation and operations in vacuo can not be conducted in a continuous process because of differences in the working environments. Further, it is necessary to effect evacuation twice.